Self-contained breathing apparatuses (SCBA's) are well-known in the art. These devices are used extensively by firefighters in fire fighting. To ensure safety in use, both the integrity of the equipment and a person's ability to use the equipment must be continuously monitored and tested.
SCBA's are all equipped with pressure gauges to permit a user to monitor the remaining volume of available air in the air tank. Although digital displays for pressure gauges have been provided, analog gauges are most commonly used. Regardless of the types of pressure gauges mounted to the apparatus itself, the gauges are relatively crude in that precise measurements are generally not provided. Precision in these devices is sacrificed for durability and toughness due to exposure to hazardous environments.
Firefighters are issued a low air alarm as standard equipment. The low air alarm provides an indication that a SCBA is at a dangerously low level of air. Firefighters are trained to call for help upon activation of the low air alarm because insufficient air may be present to provide for proper escape from a fire or hazardous situation. The NFPA (National Fire Protection Association) has tracked non-heart related deaths of firefighters inside structure fires since 1978 and has found that smoke inhalation has been the number one cause of death each year since that time.
A major reason for smoke inhalation deaths among firefighters is the unexpected depletion of air supply. In spite of being provided with various gauges and alarms, a firefighter may deplete an air supply much faster than anticipated. Standard firefighter SCBA's are issued as 30-minute or 45-minute supplies, and, as such, a time element is associated with air supply. However, an actual air supply may only last two-thirds of the allotted time. The shortage of air supply may be attributed to insufficient filling, particularly where errant pressure gauges are used, showing a higher pressure lever than actual (higher pressure reading indicates higher volume of air). Likewise, filling at elevated temperature may present a higher pressure level than actual, with a cooling of the air to ambient providing a lower than expected air volume. Filling SCBA's in succession may lead to filling equipment becoming hot and thrown off pressure measurements. In addition, a firefighter's mask may have a poor seal, causing undesired leakage, and the actual physical condition and breathing technique of the firefighter must be also taken into consideration.
Breathing methods have been developed in the prior art to prolong a SCBA air supply. One such technique known as “skip breathing” calls for intermittently holding one's breath during respiration. However, this technique has been found to increase levels of carbon dioxide in one's blood and is of questionable value. A more effective technique has been developed known as the Reilly-Emergency Breathing Technique (R-EBT) which involves normal inhalation, but humming upon exhalation. This technique has been practiced by firefighters and effective extension of SCBA air supply has been found. In particular, under same use conditions by the same firefighters, it has been found that the R-EBT technique allows for a fixed air supply to last longer than with a normal breathing technique. To allow for effective use for this breathing technique, as well as any other breathing technique, comparative testing and training must be conducted wherein firefighters may be tested against their own results, as well as, the results of others.
Cascade systems and manifold carts are known in the art for simultaneously filling several SCBA's. However, residual pressure in the manifold causes SCBA-to-SCBA pressure fluctuation especially upon sequential closing of the SCBA's. As such, these prior art systems do not permit accurate equal filling amongst a plurality of SCBA's. Without equal filling, a base line for comparative testing cannot be established.